The present invention relates to a cryogenic/refrigerant tool and method for freezing the content of a pipe, preferably in an invasive manner. Hereinafter, the term "cryogenic" is used in its broadest sense. It encompasses not only subject matter involving super-cooled fluids, but also subject matter involving refrigerants instead of super-cooled fluids, regardless of whether applied using an open flow arrangement or a closed refrigeration loop.
There are various situations where it is desirable to terminate the flow of fluids through a pipe. One example involves defective valve replacement. When a valve leaks, routine maintenance of equipment, or replacement of the valve generally is not practical without shutting down the entire system and draining the pipe. Shutting down of the entire system, however, is not practical when critical operations must be maintained using the system.
A second example is where a valve was not installed in a branch line during original construction, but must be installed now in the pipe without shutting down the entire system. In either case, a freeze of the pipe contents would be desirable upstream and downstream of the desired valve site in order to prevent loss of fluid, chemical treatment, or both. In addition to advantageously avoiding drainage of the system, freezing would eliminate the need for refilling and venting of air from elements of the fluid network (e.g., heat transfer equipment and coils).
With the foregoing difficulties as a background, several devices and methods have been developed for plugging an existing pipe to stop the flow of fluid through the pipe. Some of those devices and techniques involve insertion of a plug through a hole in the pipe or otherwise, and in some cases, inflation of the plug after insertion. At least one device and technique involves freezing of the material which is used to inflate the plug and/or external application of a cooling device to the pipe which assists in freezing of the material in the plug.
Still other devices and techniques provide only a cooling device to an outside surface of the pipe. Such devices draw heat from the contents of the pipe, through the pipe itself, and eventually freeze the contents of the pipe to form a plug. Such devices and techniques, however, are not always effective or practical. When the content of the pipe continues to flow (e.g., because of leakage or otherwise), the heat introduced by the additional flow either prevents freezing, or extends the freezing time to such an extent that it becomes economically impractical.
Several problems also are associated with the conventional plugging techniques. With regard to the devices and techniques which insert a plug into the contents of the pipe, for example, the use of such devices and techniques is limited to those pipes which are compatible with the size and shape of the plug. If a wide range of pipe sizes and shapes are to be plugged, multiple plugs must be provided, each having a different size and/or shape. If the material which makes up the plug is flexible and/or the plug is inflatable, then care must be taken to ensure that such material is compatible with the contents of the various pipes into which the plugs will be inserted. The process of inserting and/or inflating the plug also can be rather complicated.
The devices and techniques involving application of a cooling device externally to the pipe also provide less than optimal results. In particular, heat from the contents of the pipe must be transmitted through the wall of the pipe. Such devices and techniques therefore can be slow and/or ineffective at freezing the contents of a pipe, especially when used on pipes which are constructed of more thermally insulative material and/or when the content of the pipes continues to flow, as indicated above.
There is consequently a need in the art for a device and/or method capable of locally preventing flow through a pipe, by freezing the content of pipe, without the need for insertion and inflation of a plug, and without being limited to thermally conductive pipes or pipes in which the content does not flow.